1. Field of the Invention
The present invention relates to an optical wavelength converter system, and more particularly to an optical wavelength converter system employing a optical wavelength converter device made of a bulk single-crystal of organic nonlinear optical material for converting the wavelength of a semiconductor laser beam into the wavelength of a second harmonic wave.
2. Description of the Prior Art
Japanese Unexamined Patent Publication No. 63(1988)-121829, for example, discloses an optical wavelength converter device for converting the wavelength of a laser beam which is emitted as a fundamental wave from a semiconductor laser equipped with an external resonator, into the wavelength of a second harmonic wave thereof (i.e., for shortening the wavelength of the laser beam).
As disclosed in Japanese Unexamined Patent Publication No. 62(1987)-189783, there is known a laser-diode-pumped solid-state laser in which a solid-state laser rod doped with a rare-earth material such as neodymium is pumped by a semiconductor laser. In order to obtain a laser beam having a shorter wavelength, a bulk single-crystal of nonlinear optical material is disposed in a resonator for converting the wavelength of a laser beam which is oscillated by the solid-state laser into the wavelength of a second harmonic wave.
Since the conventional laser-diode-pumped solid-state lasers with the wavelength conversion capability employ inorganic nonlinear optical materials such as KTP, LiNbO.sub.3, etc., their wavelength conversion efficiency is low. This problem holds true for the aforesaid optical wavelength converter device which uses a semiconductor laser with an external resonator as a fundamental wave source.
As shown in Japanese Unexamined Patent Publication No. 63(1988)-121829, it has also been proposed to use an optical waveguide of inorganic nonlinear optical material. While the optical wavelength conversion efficiency of such an optical waveguide is high because of an increased optical power density of a fundamental wave, it is difficult to introduce the fundamental wave into the optical waveguide. An optical wavelength converter device of such arrangement is not yet practical enough since accurate control over the temperature, the magnetic field, and the ultrasonic energy is necessary in view of very strict conditions needed for phase matching between the fundamental wave and the wavelength-converted wave.
The optical wavelength converter device which comprises a laser-diode-pumped solid-state laser and a bulk single-crystal of nonlinear optical material is large in size since it employs a solid-state laser rod.